title: Site-specific differences in bone mineral density in black and white premenopausal South African women.
abstract: CONCLUSIONS
  We examined ethnic differences in bone mineral density (BMD) and the contribution of body composition, lifestyle and socioeconomic factors in South African women. Femoral neck and total hip BMD were higher, but lumbar spine BMD was lower in black women, with body composition, lifestyle and socioeconomic status (SES) factors contributing differently in ethnic groups.
  
  
  BACKGROUND
  There is a paucity of data on the relative contribution of body composition, lifestyle factors and SES, unique to different ethnic groups in South Africa, to BMD. We examined differences in femoral neck (FN), total hip (TH) and lumbar spine (LS) BMD between black and white premenopausal South African women and the associations between BMD and body composition, lifestyle factors and SES in these two ethnic groups.
  
  
  METHODS
  BMD and body composition were measured in 240 black (27 ± 7; 18-45 years) and 187 white (31 ± 8; 18-45 years) women using dual-energy X-ray absorptiometry. Questionnaires were administered to examine SES, physical activity and dietary intake.
  
  
  RESULTS
  After co-varying for age, FN and TH were higher in black than white women (FN 0.882 ± 0.128 vs. 0.827 ± 0.116 g/cm(2), P < 0.001; TH 0.970 ± 0.130 vs. 0.943 ± 0.124 g/cm(2), P = 0.018). When adjusting for ethnic differences in body composition, LS was higher in white than black women. In black women, fat-free soft tissue mass, SES and injectable contraceptive use explained 33-42% of the variance in BMD at the hip sites and 22% at the LS. In white women, fat-free soft tissue mass and leisure activity explained 24-30% of the variance in BMD at the hip sites, whereas fat mass, leisure activity and oral contraceptive use explained 11% of the variance at the LS.
  
  
  CONCLUSIONS
  FN and TH BMD were higher, but LS BMD was lower in black than white South African women with body composition, lifestyle and SES factors contributing differently to BMD in these women.
authors.affiliation: UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, P.O. Box 115, Newlands 7725, South Africa.
authors.forename: S
authors.initials: S
authors.lastname: Chantler
authors.forename: K
authors.initials: K
authors.lastname: Dickie
authors.forename: J H
authors.initials: JH
authors.lastname: Goedecke
authors.forename: N S
authors.initials: NS
authors.lastname: Levitt
authors.forename: E V
authors.initials: EV
authors.lastname: Lambert
authors.forename: J
authors.initials: J
authors.lastname: Evans
authors.forename: Y
authors.initials: Y
authors.lastname: Joffe
authors.forename: L K
authors.initials: LK
authors.lastname: Micklesfield
mesh_terms: D000293:Adolescent; D000328:Adult; D044383:Black People / Q000706:statistics & numerical data*; D001823:Body Composition; D015519:Bone Density / Q000502:physiology*; D005260:Female; D005272:Femur Neck / Q000502:physiology; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism; D008019:Life Style; D008159:Lumbar Vertebrae / Q000502:physiology; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology; D017697:Premenopause / Q000208:ethnology* / Q000502:physiology; D060728:Reproductive Health; D012959:Socioeconomic Factors; D013019:South Africa; D044465:White People / Q000706:statistics & numerical data*; D055815:Young Adult
chemical_list: D018836:Inflammation Mediators